He has been in the comic strip field since 1950, working on such strips as Kerry Drake, Little Iodine and Bunny. In comic books, he was the last artist for Little Lulu before it was cancelled in 1984. He took over The Katzenjammer Kids in 1986 and the Popeye Sunday strip in 1994.
Eisman became a teacher at the Joe Kubert School of Cartoon and Graphic Art in 1976. An extensive interview with Eisman on his career appeared in Hogan's Alley #15 (2007). In December 2008, Eisman was the first to introduce the character of Bluto to the Popeye Sunday page. Bluto has continued to appear as the twin brother of Brutus.
He won the 1983 National Cartoonists Society Award for Best Comic Book.